Method of producing iron ore concentrates by froth flotation

ABSTRACT

Iron ore concentrates can be obtained by the flotation of iron ores providing mixtures containing at least one ether canine of formula (I): 
     
         R.sup.1 O--(C.sub.n H.sub.2n).sub.y --NH--(C.sub.m H.sub.2m --NH).sub.x H, 
    
     in which R 1  is a linear or branched chain aliphatic hydrocarbon moiety having 6 to 22 carbon atoms and 0, 1, 2 or 3 double bonds; n and m independently of one another represent the number 1, 2 or 3; x=0 or the number 1, 2 or 3; and y=2 or 3, and at least one other anionic and/or nonionic collector.

FIELD OF THE INVENTION

This invention relates to a process for the production of iron oreconcentrates by flotation of iron ores, in which mixtures of specialether amines with anionic and/or nonionic collectors are used ascollectors.

PRIOR ART

Iron ores occur in nature mostly in the form of oxides, among whichmagnetite, hematite, martite, limonite and goethite are the most wellknown. These oxides mainly contain silicates, more particularly quartz,and also phosphorus and sulfur compounds as impurities. For theproduction of high-quality steel, the impurities mentioned have to beremoved from the iron ores; this is generally done by flotation.

To this end, the iron ore is normally first size-reduced and dry-groundbut preferably wet-ground and suspended in water. A collector is thenadded, often in conjunction with other reagents, including frothers,regulators, deactivators and/or activators, to support removal of thevaluable minerals from the gangue minerals of the ore in the subsequentflotation stage. Before air is injected into the suspension to producefoam at its surface and to initiate the flotation process, thesereagents are normally left to act on the finely ground ore for a certaintime (conditioning). The collector hydrophobicizes the surface of theimpurities present in the iron ore, so that the minerals adhere to thegas bubbles formed during aeration. The mineral components areselectively hydrophobicized so that the gangue is floated out and theconcentrate remains behind as the residue (indirect flotation).

In the flotation of iron ores, aminic compounds are preferably used ascollectors. Their function is to be selectively adsorbed onto thesurface of the impurities to ensure high depletion of these unwantedconstituents in the flotation concentrate. In addition, the collectorsare intended to form a stable, but not overly stable, flotation foam.

U.S. Pat. No. 4,168,227 describes a process for the removal of silicateimpurities from iron ores in which alkylamines, alkylenediamines andether amines are used as collectors.

According to Australian patent AU 86/53 766, the removal of silicatesand phosphates from iron ores by flotation is carried out with collectormixtures containing ether amines and ether carboxylic acid amides.

The use of anionic surfactants as collectors or co-collectors in theflotation of nonsulfide ores is known from a number of publications.Corresponding examples are alkyl phosphates and alkylether phosphates[Erzmetall {Title in English: Heavy Metal} 30, 505 (1977)], ethercarboxylic acids [DE 22 37 359 A1], sulfosuccinamides and succinamates[U.S. Pat. Nos. 4,206,045; 4,309,282 and 4,139,481] and alkyl asparticacids [EP 0 270 018 A1].

However, the purification of iron ores by flotation to form concentrateswhich satisfy the increasing quality requirements of industry is stillproblematical. In particular, there are no collector systems with whichiron ore concentrates containing less than 0.015% by weight ofphosphorus can be produced.

OBJECT OF THE INVENTION

Accordingly, the problem addressed by the present invention was toprovide an improved flotation process for the production of iron oreconcentrates which would not be attended by any of the disadvantagesmentioned above.

DESCRIPTION OF THE INVENTION

The present invention relates to a process for the production of ironore concentrates by flotation, in which crushed iron ore is mixed withwater to form a suspension, air is introduced into the suspension in thepresence of a reagent system, and the froth formed is removed togetherwith the solids floated therein, characterized in that mixturescontaining

a) at least one ether amine corresponding to formula (I):

    R.sup.1 O--(C.sub.n H.sub.2n).sub.y --NH--(C.sub.m H.sub.2m --NH).sub.x H(I),

in which R¹ is a linear or branched aliphatic hydrocarbon moiety having6 to 22 carbon atoms and 0, 1, 2 or 3 double bonds; n and mindependently of one another represent the number 1, 2 or 3; x=0 or thenumber 1, 2 or 3; and y=2 or 3, and

b) at least one other anionic and/or nonionic collector are used ascollectors.

It has surprisingly been found that the collector mixtures to be used inaccordance with the invention are capable of selectively removingphosphorus impurities from iron ores without any adverse effect on thecationic flotation of the silicates. The invention includes theobservation that phosphorus flotation and silicate flotation can becarried out both separately and also in a single step. In particular, ithas been found that the concentrates obtainable by the process accordingto the invention have phosphorus contents of less than 0.015% by weight,based on the concentrate.

Ether amines corresponding to formula (I) are known compounds which maybe obtained by the relevant methods of preparative organic chemistry.They are normally produced from fatty alcohol sulfates which are reactedwith alkanolamines or aminoalkyl alkanolamines at temperatures of around180° C. in the presence of alkali metal hydroxides, alkali metal sulfatebeing formed as a secondary product [DE 35 04 242 A1].

Starting materials for the ether amines to be used in accordance withthe invention are fatty alcohol sulfates based on saturated orunsaturated fatty alcohols and also primary amines and diamines. Typicalexamples are reaction products of octyl sulfate, decyl sulfate, laurylsulfate, myristyl sulfate, cetyl sulfate, stearyl sulfate, oleylsulfate, elaidyl sulfate, petroselinyl sulfate, linolyl sulfate,linolenyl sulfate, arachyl sulfate, gadoleyl sulfate, behenyl sulfateand erucyl sulfate with methanolamine, ethanolamine, n-propanolamine,i-propanolamine, aminoethyl ethanolamine, aminoethyl propanolamine,aminopropyl ethanolamine and aminopropyl propanolamine. As usual inoleochemistry, sulfates based on technical fatty alcohol cuts may alsobe reacted with the amines mentioned. Ether amines of formula (I), inwhich R¹ is an alkyl moiety having 6 to 18 and, more particularly, 8 to12 carbon atoms, are preferred.

Anionic collectors in the context of the invention are anionicsurfactants of the fatty acid, alkyl sulfate, alkyl ether sulfate, alkylsulfosuccinate, alkyl sulfosuccinamate, alkyl benzenesulfonate, alkanesulfonate, petroleum sulfonate, acryl lactylate, sarcoside, alkylphosphate, alkylether phosphate, alkyl aspartic acid and ethercarboxylic acid types. All these anionic surfactants are known compoundsof which the production--unless other otherwise stated--is described,for example, in J. Falbe, U. Hasserodt (ed.), Katalysatoren, Tenside undMineraloladditive [Title in English: Catalysts, Surfactants, and MineralOil Additives] (Thieme Verlag, Stuttgart, 1978) and in J. Falbe (ed.),Surfactants in Consumer Products (Springer Verlag, Berlin, 1986).

The fatty acids used are, above all, the linear fatty acids obtainedfrom vegetable or animal fats and oils, for example by hydrolysis andoptionally fractionation and/or separation by the rolling-up process;these fatty acids correspond to formula (II):

    R.sup.2 COOY                                               (II),

in which R² is an aliphatic hydrocarbon moiety having 12 to 18 carbonatoms and 0, 1, 2 or 3 double bonds and Y is an alkali metal, alkalineearth metal or ammonium ion. Particular significance is attributed tothe sodium and potassium salts of oleic acid and tall oil fatty acid.

Suitable alkyl sulfates are the water-soluble salts of sulfuric acidsemiesters of fatty alcohols corresponding to formula (III):

    R.sup.3 --O--SO.sub.3 Z                                    (III),

in which R³ is a linear or branched alkyl moiety having 8 to 22 andpreferably 12 to 18 carbon atoms and Z is an alkali metal or an ammoniumion.

Suitable alkylether sulfates are the water-soluble salts of sulfuricacid semiesters of fatty alcohol polyglycol ethers corresponding toformula (IV): ##STR1## in which R⁴ is a linear or branched alkyl moietyhaving 8 to 22 and preferably 12 to 18 carbon atoms, R⁵ is hydrogen or amethyl group and n=1 to 30, preferably 2 to 15, and Z is as definedabove.

Suitable alkyl sulfosuccinates are sulfosuccinic acid monoesters offatty alcohols corresponding to formula (V): ##STR2## in which R⁶ is alinear or branched alkyl moiety having 8 to 22 and preferably 12 to 18carbon atoms and Z is as defined above.

Suitable alkyl sulfosuccinamates are sulfosuccinic acid monoamides offatty amines corresponding to formula (VI): ##STR3## in which R⁷ is alinear or branched alkyl moiety having 8 to 22 and preferably 12 to 18carbon atoms and Z is as defined above.

Suitable alkylbenzene sulfonates are substances corresponding to formula(VII):

    R.sup.8 --C.sub.6 H.sub.4 --SO.sub.3 Z                     (VII),

in which R⁸ is a linear or branched alkyl moiety having 4 to 16 andpreferably 8 to 12 carbon atoms and Z is as defined above.

Suitable, alkane sulfonates are substances corresponding to formula(VIII):

    R.sup.9 --SO.sub.3 Z                                       (VIII),

in which R⁹ is a linear or branched alkyl moiety having 12 to 18 carbonatoms and Z is as defined above.

Suitable petroleum sulfonates are substances obtained by reaction oflubricating oil fractions with sulfur trioxide or oleum and subsequentneutralization with sodium hydroxide. Products in which the hydrocarbonmoieties mainly have chain lengths of 8 to 22 carbon atoms areparticularly suitable.

Suitable acyl lactylates are substances corresponding to formula (IX):##STR4## in which R¹⁰ is an aliphatic, cycloaliphatic or alicyclic,optionally hydroxyl-substituted hydrocarbon moiety having 7 to 23 carbonatoms and 0, 1, 2 or 3 double bonds and Z is as defined above. Theproduction and use of acyl lactylates in flotation is described inGerman patent application DE 32 38 060 A1.

Suitable sarcosides are substances corresponding to formula (X):##STR5## in which R¹¹ is an aliphatic hydrocarbon moiety having 12 to 22carbon atoms and 0, 1, 2 or 3 double bonds.

Suitable alkyl phosphates and alkylether phosphates are substancescorresponding to formulae (XI) and (XII): ##STR6## in which R¹² and R¹³independently of one another represent an alkyl or alkenyl moiety having8 to 22 carbon atoms and p and q have a value of 0 in the case of thealkyl phosphates and a value of 1 to 15 in the case of the alkyletherphosphates and Z is as defined above.

If the ether amines are used in admixture with alkyl phosphates oralkylether phosphates in accordance with the invention, the phosphatesmay be present as monophosphates or diphosphates. In this case, mixturesof monophosphates and dialkyl phosphates such as are formed in theindustrial production of such compounds are preferably used.

Alkyl aspartic acids are understood to be compounds corresponding toformula (XIII): ##STR7## in which R¹⁴ is an alkyl or alkenyl moietyhaving 8 to 22 carbon atoms and Z is as defined above.

Finally, ether carboxylic acids are compounds corresponding to formula(XIV):

    R.sup.15 O--(CH.sub.2 CH.sub.2 O).sub.n --CH.sub.2 --COOZ  (XIV),

in which R¹⁵ is an alkyl or alkenyl moiety having 8 to 22 carbon atomsand n is 0 or a number of 1 to 10 and Z is as defined above.

Nonionic collectors in the context of the invention are nonionicsurfactants of the fatty alcohol polyglycol ether, alkylphenolpolyglycol ether, fatty acid polyglycol ester, fatty acid amidepolyglycol ether, fatty amine polyglycol ether, mixed ether, hydroxymixed ether and alkyl glycoside types. All these nonionic surfactantsare known compounds of which the production--unless otherwise stated--isdescribed, for example, in J. Falbe, U. Hasserodt (ed.), Katalysatoren,Tenside und Mineraloladditive [Title in English: Catalysts, Surfactants,and Mineral Oil Additives] (Thieme Verlag, Stuttgart, 1978) and in J.Falbe (ed.), Surfactants in Consumer Products (Springer Verlag, Berlin,1986).

Suitable fatty alcohol polyglycol ethers are adducts of on average nmoles of ethylene and/or propylene oxide with fatty alcohols whichcorrespond to formula (XV): ##STR8## in which R¹⁶ is a linear orbranched alkyl moiety having 8 to 22 and preferably 12 to 18 carbonatoms, R⁵ is hydrogen or a methyl group and n is a number of 1 to 30 andpreferably 2 to 15.

Suitable alkylphenol polyglycol ethers are adducts of on average n molesof ethylene and/or propylene glycol with alkylphenols which correspondto formula (XVI): ##STR9## in which R¹⁷ is an alkyl moiety having 4 to15 and preferably 8 to 10 carbon atoms and R⁵ and n are as definedabove.

Suitable fatty acid polyglycol esters are adducts of on average n molesof ethylene oxide and/or propylene oxide with fatty acids whichcorrespond to formula (XVII): ##STR10## in which R¹⁸ is an aliphatichydrocarbon moiety having 5 to 21 carbon atoms and 0, 1, 2 or 3 doublebonds and R⁵ and n are as defined above.

Suitable fatty acid amidopolyglycol ethers are adducts of on average nmoles of ethylene and/or propylene oxide with fatty acid amides whichcorrespond to formula (XVIII): ##STR11## in which R¹⁹ is an aliphatichydrocarbon moiety having 5 to 21 carbon atoms and 0, 1, 2 or 3 doublebonds and R⁵ and n are as defined above.

Suitable fatty amine polyglycol ethers are adducts of on average n molesof ethylene stud/or propylene oxide with fatty amines which correspondto formula (XIX): ##STR12## in which R²⁰ is an alkyl moiety having 6 to22 carbon atoms and R⁵ and n are as defined above.

Suitable mixed ethers are reaction products of fatty alcohol polyglycolethers with alkyl chlorides corresponding to formula (XX): ##STR13## inwhich R²¹ is an aliphatic hydrocarbon moiety having 6 to 22 carbon atomsand 0, 1, 2 or 3 double bonds, R²² is an alkyl moiety having 1 to 4carbon atoms or a benzyl moiety and R⁵ and n are as defined above.

Suitable hydroxy mixed ethers are substances corresponding to formula(XXI): ##STR14## in which R²³ is an alkyl moiety having 6 to 16 carbonatoms, R²⁴ is an alkyl moiety having 1 to 4 carbon atoms or a benzylmoiety and R⁵ and n are as defined above. The production of the hydroxymixed ethers is described in German patent application DE 37 23 323 A1.

Suitable alkyl glycosides are substances corresponding to formula(XXII):

    R.sup.25 --O--(G).sub.x                                    (XXII),

in which G stands for a glycose unit derived from a sugar having 5 or 6carbon atoms, x is a number of 1 to 10 and R²⁵ is an aliphatichydrocarbon moiety having 6 to 22 carbon atoms and 0, 1, 2 or 3 doublebonds. G preferably stands for a glucose unit and x is preferably anumber of 1.1 to 1.6. The production of the alkyl glycosides isdescribed, for example, in German patent application DE 37 23 826 A1.

The mixtures of the ether amines with the anionic and/or nonioniccollectors may have a content of 5 to 95% by weight and preferably 10 to60% by weight of the ether amines. Particularly advantageous results areobtained with mixtures which, besides ether amines, contain fatty acids,alkyl aspartic acids and/or ether carboxylic acids or alkylsulfosuccinamates, alkyl phosphates and/or alkylether phosphates.

To obtain economically useful results in the flotation of iron ore, thecollector mixture has to be used in a certain minimum quantity. At thesame time, however, there is a maximum quantity which must not beexceeded because otherwise foaming becomes excessive and selectivitytowards the impurities to be floated out decreases. The quantities inwhich the collector mixtures to be used in accordance with the inventionmay be employed are normally from 20 to 2,000 g and preferably from 50to 1,000 g per tonne of crude ore.

The process according to the invention includes the use of typicalflotation reagents, such as for example frothers, regulators,activators, deactivators, etc. The flotation process is carried outunder the same conditions as known processes. Information on thetechnological background of ore preparation can be found in thefollowing literature references: H. Schubert, Aufbereitung festermineralischer Stoffe [Title in English: Separation of MineralSubstances] (Leipzig, 1967); D. B. Puchas (Ed.), Solid/Liquid SeparationEquipment Scale-Up (Croydon, 1977); E. S. Perry, C. J. VanOss, E.Grushka (Ed.), Separation and Purification Methods (New York,1973-1978).

The following Examples are intended to illustrate the invention withoutlimiting it in any way.

Examples

I. Collectors used and collectors

                  TABLE 1                                                         ______________________________________                                        Collectors                                                                           Aminic collectors                                                      ______________________________________                                        A1)      Ether amine based on                                                          n-propylamine and C.sub.8-10 fatty alcohol sulfate                            (C.sub.8-10 H.sub.17-21)-O-(CH.sub.2).sub.3 NH.sub.2                 A2)      Ether amine based on                                                          n-propylamine and C.sub.8-12 fatty alcohol sulfate                            (C.sub.8-12 H.sub.17-25)-O-(CH.sub.2).sub.3 -NH.sub.2                A3)      Ether amine based on                                                          Aminopropyl propanolamine and decyl sulfate                                   C.sub.10 H.sub.21 -O-(CH.sub.2).sub.3 -NH-(CH.sub.2).sub.3                    -NH.sub.2                                                            ______________________________________                                    

                  TABLE 2                                                         ______________________________________                                        Collectors                                                                    Anionic and nonionic collectors                                               ______________________________________                                        B1)  Ether phosphate sodium salt                                                   based on C.sub.12-14 coconut oil fatty alcohol; n = 1,2                       [(C.sub.12-14 H.sub.25-29)(OCH.sub.2 CH.sub.2).sub.10 O].sub.n                PO(ONa).sub.3-n'                                                         B2)  Ether carboxylic acid sodium salt based on                                    C.sub.12-18 coconut oil fatty alcohol 7 EO adduct                             (C.sub.12-18 H.sub.25-37)O(CH.sub.2 CH.sub.2 O).sub.7 CH.sub.2                COONa                                                                    B3)  N-tallow alkyl sulfosuoccinamide disodium salt                                 ##STR15##                                                               B4)  N-tallow alkyl aspartic acid disodium salt                                     ##STR16##                                                               B5)  C.sub.12-18 coconut oil fatty alcohol 2EO,4PO adduct                           ##STR17##                                                               B6)  Hydrolyzed rapeseed oil fatty acid                                            Fatty acid mixture containing >80% by weight                                  oleic acid                                                               B7)  Tallow alkyl sulfosuccinate disodium salt                                      ##STR18##                                                               ______________________________________                                    

II. Ores used

Two North American hematite samples and a magnetite ore were used forthe tests. In addition to iron oxide, the hematite ore containedapproximately 44% by weight of silicates (mainly quartz) and 0.1 to 0.2%by weight of apatite. The exact chemical analysis of the ore samplesused is shown in Table 3:

                  TABLE 3                                                         ______________________________________                                        Analysis of the ore samples (mean values)                                                 Fe         P          SiO.sub.2                                   Ore type    % by weight                                                                              % by weight                                                                              % by weight                                 ______________________________________                                        Hematite sample I                                                                         35.9       0.038      43.9                                        Hematite sample II                                                                        38.4       0.025      44.8                                        Magnetite   65.0       0.015      7.0                                         ______________________________________                                    

III. Flotation examples for hematite ore

Preparation involved the following steps:

grinding,

selective desludging and

rougher flotation.

The aminic collectors and the anionic and/or nonionic collectors wereused in the rougher flotation stage.

600 g of the ore, coarsely size-reduced beforehand, were ground in a barmill for 45 minutes in the presence of 13.4 mg of sodium metasilicate,40.2 mg of sodium hydroxide and approximately 400 ml of flotation water(hardness: 14.7 mg/l CaCl₂ •2H₂ O and 4.9 mg/l MgSO₄ •7H₂ O). The groundore had the following particle size distribution:

>31 μm: 7.7% by weight

11 to 31 μm: 45.3% by weight

<11 μm: 47.0% by weight.

The finely ground ore was then transferred to the desludging stage anddiluted to approximately 8 liters (solids content: 7% by weight). 3 mlof heat-treated cornstarch (2.25% by weight) were then added and thesupernatant sludge was removed after 2 minutes.

The desludged flotation batch (volume: approximately 1 l) wastransferred to a 2 liter stirred Denver cell (type D1). 67 ml of sodiumhydroxide and 12 ml of cornstarch (2.25% by weight) were then added, thecell was filled with flotation water and the liquid with solid materialin suspension was conditioned while stirring for 2 minutes. The aminiccollector and the anionic and/or nonionic collectors were thenintroduced. The rougher flotation stage was then carded out at a stirrerspeed of 1,200 r.p.m., a foam product and a concentrate being obtainedin the cell. After the addition of more collector, flotation was carriedout for a second time; another foam product and the desired iron oreconcentrate were obtained. Particulars of the flotation tests can befound in Tables 4, 5 and 6.

                  TABLE 4a                                                        ______________________________________                                        Hematite, sample I:                                                           Collector systems and quantities used                                                 Quantity used                                                              Collector                                                                              FS I    FS II  Collector                                                                             Quantity used                            Ex.  A        g/t     g/t    B       g/t                                      ______________________________________                                        1    A1       48      48     B1       90                                      2    A1       48      48     B1      180                                      3    A1       48      96     B1      180                                      4    A2       48      48     B2      126                                      5    A1       48      48     B3       60                                      6    A1       48      48     B1/B3   60/60                                    7    A1       32      32     B1/B3   80/9                                     8    A1       32      32     B1/B3   80/9                                     9    A1       48      48     B1/B3   39/39                                    10   A1       36      48     B1/B3   45/45                                    11   A1       36      48     B1/B3   60/60                                    C1   A1       48      48     --      --                                       ______________________________________                                    

                  TABLE 4b                                                        ______________________________________                                        Hematite, sample II:                                                          Collector and quantities used                                                         Quantity used                                                              Collector                                                                              FS I    FS II  Collector                                                                             Quantity used                            Ex.  A        g/t     g/t    B       g/t                                      ______________________________________                                        12   A1       48      48     B1/B3   60/60                                    13   A1       48      48     B1/B3   84/36                                    14   A1       48      96     B1/B3   96/24                                    15   A1       48      48     B1/B3   108/12                                   16   A1       48      48     B1/B3   48/72                                    17   A1       48      48     B4/B5/B6                                                                              24/40/80                                 18   A1       48      48     B4/B5/B6                                                                              10/34/100                                19   A1       48      48     B4/B5/B6                                                                              28/21/95                                 20   A1       48      48     B4/B5/B6                                                                              20/57/67                                 C2   A1       48      48     --      --                                       ______________________________________                                         Legend: FS I: Flotation stage I                                               FS II: FLotation stage II                                                

                  TABLE 5a                                                        ______________________________________                                        Hematite, sample I:                                                           Desludging results                                                            Percentages as % by weight                                                    Sludge                    Batch                                                      Quantity   Fe     P       SiO.sub.2                                                                          P                                       Ex.    %          %      %       %    %                                       ______________________________________                                        1      30.2       12.8   0.051   75.8 0.038                                   2      29.9       12.6   0.055   76.1 0.039                                   3      29.9       12.6   0.055   76.1 0.039                                   4      29.6       12.8   0.049   73.1 0.036                                   5      26.9       13.3   0.052   76.4 0.034                                   6      26.9       13.9   0.053   77.8 0.035                                   7      28.1       12.1   0.058   75.2 0.038                                   8      27.1       12.6   0.055   75.0 0.037                                   9      27.2       13.9   0.055   77.9 0.037                                   10     29.8       11.4   0.057   76.8 0.039                                   11     31.5       11.1   0.053   74.3 0.039                                   C1     29.2       13.7   0.057   74.8 0.038                                   ______________________________________                                    

                  TABLE 5b                                                        ______________________________________                                        Hematite, sample II:                                                          Desludging results                                                            Percentages as % by weight                                                    Sludge                    Batch                                                      Quantity   Fe     P       SiO.sub.2                                                                          P                                       Ex.    %          %      %       %    %                                       ______________________________________                                        12     27.3       8.5    0.054   88.8 0.026                                   13     28.6       9.9    0.052   86.1 0.027                                   14     31.9       10.1   0.046   78.1 0.025                                   15     28.3       8.6    0.050   82.4 0.025                                   16     30.9       10.1   0.047   83.4 0.026                                   17     29.6       10.3   0.050   81.9 0.026                                   18     30.7       9.9    0.045   79.7 0.024                                   19     30.6       9.9    0.046   82.4 0.025                                   20     30.2       9.5    0.048   85.7 0.025                                   C2     26.0       8.6    0.053   85.8 0.025                                   ______________________________________                                    

                  TABLE 6a                                                        ______________________________________                                        Hematite, sample I:                                                           Concentrations based on mill batch                                            Percentages as % by weight                                                    Iron concentrate          Recovery                                                 TC     Quantity  Fe    SiO.sub.2                                                                           P     Fe                                    Ex.  min.   %         %     %     %     %                                     ______________________________________                                        1    2      39.8      67.8  5.5   0.035 72.5                                  2    2      41.5      66.5  6.2   0.032 75.3                                  3    2      38.0      68.1  3.9   0.031 70.6                                  4    0      30.2      67.9  6.0   0.032 55.0                                  5    0      36.9      67.2  5.6   0.029 65.9                                  6    4      38.1      68.4  5.9   0.028 68.4                                  7    0      38.9      65.4  4.9   0.029 70.7                                  8    0      31.5      66.1  3.6   0.025 58.0                                  9    2      37.9      70.1  3.8   0.034 69.5                                  10   0      34.9      65.5  4.1   0.030 64.0                                  11   0      33.8      66.6  4.1   0.029 63.1                                  C1   0      33.9      66.8  5.0   0.044 60.6                                  ______________________________________                                    

                  TABLE 6b                                                        ______________________________________                                        Hematite, sample II:                                                          Concentrations based on mill batch                                            Percentages as % by weight                                                    Iron concentrate          Recovery                                                 TC     Quantity  Fe    SiO.sub.2                                                                           P     Fe                                    Ex.  min.   %         %     %     %     %                                     ______________________________________                                        12   0      32.8      69.8  3.1   0.012 57.4                                  13   0      31.8      68.8  2.7   0.013 56.1                                  14   0      33.4      68.5  2.3   0.012 60.2                                  15   0      33.5      68.4  2.4   0.012 60.1                                  16   0      31.7      67.7  3.2   0.013 56.5                                  17   0      31.5      68.2  3.1   0.011 55.2                                  18   0      30.9      68.1  3.4   0.010 55.1                                  19   0      31.0      67.5  3.5   0.010 55.3                                  20   0      31.9      68.2  3.5   0.014 57.3                                  C2   0      32.4      70.2  2.5   0.021 57.5                                  ______________________________________                                    

Addition sequence of the collectors [Examples];

    ______________________________________                                        a)   Rougher 1  collector A, collector B [1-5, 7, 10, 11, C1]                 b)   Rougher 1  collector A and collectors B1 and B3 [6]                      c)   Preliminary                                                                              collector B [8]                                                    flotation                                                                     Rougher 1, 2                                                                             collector A                                                   d)   Rougher 1  collector A, collector B (30/30 g/t)                               Rougher 2  collector A, collector B ( 9/9 g/t) [9]                       e)   Rougher 1  collector A, collector B, no conditioning                                     [12-20, C2]                                                   TC              total conditioning time                                       ______________________________________                                    

IV. Flotation examples for magnetite ore

A magnetite ore with the chemical composition shown in II) was used; ithad a particle size of 89% by weight <43 μm. Flotation was again carriedout in a 2-liter Denver cell (type D1) with a suspended solids densityof approximately 220 g/l in water with a calcium ion content of 4 mg/l.The pH value of the liquid with solids in suspension was adjusted to 8.5by addition of sodium hydroxide; the stirrer speed was 1,200 r.p.m.After the addition of collector and frother, air was introduced at aflow rate of 130 to 150 l/h for flotation. The foam was removed over aperiod of 2 minutes in the general silicate flotation phase, theflotation time being extended in an additional phosphate flotationphase, as shown in Table 7.

The aminic collector was added in the form of a 0.25% by weight aqueoussolution while the anionic collector mixtures were added in the form of5% by weight aqueous solutions. In all the flotation tests, a commercialfrother based on aldehydes, alcohols and esters was used in a quantityof 30 g/t, being introduced into the liquid with solids in suspension inundiluted form.

                  TABLE 7a                                                        ______________________________________                                        Magnetite:                                                                    Collector system and quantities used                                               Collector Quantity used                                                                             Collector                                                                             Quantity used                              Ex.  A         g/t         B       g/t                                        ______________________________________                                        21   A3        65          B6       95                                        22   A3        65          B7      100                                        23   A3        65          B1/B3   60/7                                       24   A3        65          B1/B3   60/7                                       25   A3        65          B4/B5/B6                                                                              9/14/28                                    26   A3        65          B4/B5/B6                                                                              9/14/28                                    27   A3        65          B1/B3   60/7                                       28   A3        65          B4/B5/B6                                                                              9/14/28                                    C3   A3        65          --      --                                         ______________________________________                                    

                  TABLE 7b                                                        ______________________________________                                        Percentages as % by weight                                                    Iron concentrate         Recovery                                                    Quantity   Fe     SiO.sub.2                                                                            P    Fe                                       Ex.    %          %      %      %    %                                        ______________________________________                                        21     87.7       67.6   4.6    0.011                                                                              91.3                                     22     91.4       68.1   4.2    0.012                                                                              95.1                                     23     86.2       68.6   3.8    0.011                                                                              89.7                                     24     92.2       67.7   4.9    0.012                                                                              94.5                                     25     88.7       68.5   4.2    0.010                                                                              91.9                                     26     89.2       68.0   4.5    0.010                                                                              92.0                                     27     91.7       67.4   4.9    0.011                                                                              94.0                                     28     91.3       66.9   4.7    0.011                                                                              93.7                                     C3     92.1       68.3   3.9    0.015                                                                              95.3                                     ______________________________________                                    

Flotation sequence and flotation times [Examples]:

a) Silicate flotation 2 mins., apatite flotation 1 min. [21-23,25,C3]

b) Apatite flotation 0.5 mins., silicate flotation 2.5 mins. [24]

c) Apatite flotation and silicate flotation together 2.5 mins. [27,28]

We claim:
 1. In a process for the removal of phosphorous from, and forthe production of, iron ore concentrates by flotation, in which crushedcrude iron ore is mixed with water and a collector to form a suspension,air is introduced into the suspension in the presence of a reagentsystem and a floated foam containing said phosphorous formed thereinalong with a flotation residue comprising an iron concentrate, whereinthe improvement comprises using as the collector, a mixturecontaining:a) from about 10 to about 60% by weight of at least one etheramine corresponding to formula (I):

    R'O--(C.sub.n H.sub.2n).sup.y --NH--(C.sub.n H.sub.2n --NH).sub.x H(I)

in which R' is a linear or branched aliphatic hydrocarbon moiety havingfrom 6 to 22 carbon atoms and 0, 1, 2 or 3 double bonds; n and mindependently of one another represent the number 1, 2 or 3; x=0 or thenumber 1, 2 or 3 and y=2 or 3; and b) the remainder being at least oneother anionic or nonionic surfactant collector, in which the anionicsurfactant collector is selected from the group consisting of fattyacids, alkyl sulfates, alkylether sulfates, alkyl sulfosuccinates,alkylsulfocinnamates, alkyl benzene sulfonates, acyl lactylates, alkylphosphates, alkylether phosphates and ether carboxylic acids, and inwhich the nonionic surfactant collector is selected from the groupconsisting of fatty alcohol polyglycol ethers, alkylphenol polyglycolethers fatty acid polyglycol esters, fatty acid amide polyglycol ethers,mixed ethers, hydroxy mixed ethers and alkyl glycosides, and in whichthe residual phosphorous content in the iron concentrate produced is nomore than 0.015% by weight based on the iron concentrate.
 2. A processas claimed in claim 1, wherein the collector mixtures contain etheramines of formula (I), in which R' is a C₆₋₁₈ alkyl moiety.
 3. A processas claimed in claim 2, wherein the collector mixtures are used inquantities of 20 to 2,000 g/t of crude iron ore.
 4. In a process for theremoval of phosphorous from, and for the production of iron oreconcentrates by flotation, in which crushed crude iron ore is mixed withwater and a collector to form a suspension, air is introduced into thesuspension in the presence of a reagent system and a floated foamcontaining said phosphorous formed therein along with a flotationresidue comprising an iron concentrate, wherein the improvementcomprises using as the collector, a mixture consisting essentially of:a)from about 10 to about 60% by weight of the collector mixture, of atleast one ether amine corresponding to formula (I):

    R'O--(C.sub.n H.sub.2n).sup.y --NH--(C.sub.n H.sub.2n --NH).sub.x H(I)

in which R' is a linear or branched aliphatic hydrocarbon moiety havingfrom 6 to 22 carbon atoms and 0, 1, 2 or 3 double bonds; n and mindependently of one another represent the number 1, 2 or 3; x=0 or thenumber 1, 2 or 3 and y=2 or 3; and b) at least one other anionicsurfactant collector (i) and/or nonionic surfactant collector (ii)selected from the group consisting of fatty alcohol polyglycol ethers,alkylphenol polyglycol ethers fatty acid polyglycol esters, fatty acidamide polyglycol ethers, mixed ethers, hydroxy mixed ethers and alkylglycosides, and in which the residual phosphorous content in the ironconcentrate produced is no more than 0.015% by weight based on the ironconcentrate.
 5. A process as claimed in claim 4, wherein the collectormixtures are used in quantities of 20 to 2,000 g/t of crude iron ore. 6.A process as claimed in claim 5, wherein R' in the ether amine formula(I) is a C₆₋₁₈ alkyl moiety.
 7. A process as claimed in claim 1, whereinthe collector mixtures are used in quantities of 20 to 2,000 g/t ofcrude iron ore.